WO2016202039A1 - Light emitting diode and preparation method thereof - Google Patents

Abstract

A light emitting diode and preparation method thereof. In one embodiment, the method comprises: forming, at a back side of a substrate (10) of a plurality of LED units (20), a plurality of impurity release holes (12); forming a plurality of invisible blown points (11) by focusing a laser on locations corresponding to the plurality of impurity release holes and located inside the substrate so as to enable communication between the impurity release holes and the invisible blown points and remove, from inside the substrate, impurity formed during the formation of the invisible blown points. As a result, the method prevents the impurity from attaching to the invisible blown points and prevents external quantum efficiency of the LED units from decreasing. In another embodiment, the method comprises: focusing on a location at inside the substrate and 10μm to 40μm from the back side of the substrate (101) so as to increase a laser energy and adjust a laser frequency, and forming holes (105) passing through the inside of the substrate by invisible laser cutting so as to expose the back side of the substrate, thereby effectively removing byproducts such as burn marks and debris after the invisible laser cutting, decreasing light absorption of the byproducts, increasing light emitting from a side wall of the LED, and enhancing luminous efficacy.

Description

 Light emitting diode and preparation method thereof

 Technical field

 [0001] The present invention belongs to the field of semiconductor fabrication, and in particular, to a light emitting diode and a method for forming the same.

 Background technique

 [0002] The cutting technology of light-emitting diodes has gradually evolved from diamond knife cutting to ordinary laser cutting. Generally, the wavelength of the laser is 355 nm or 266 nm, which is characterized in that it can draw both sapphire substrates and various films. Layers, such as gallium nitride layers, Bragg reflectors, metal layers, and the like.

 [0003] Referring to FIG. 1, a light-emitting diode cutting technique that has emerged and developed in recent years is a stealth laser cutting |J, which is characterized in that it can penetrate the sapphire substrate 10 to form energy in the sapphire substrate 10. Explosion point 11, the explosion point 11 burst and achieve the purpose of cutting. Compared with ordinary laser cutting or diamond cutting, it reduces the laser burned area on the side of the wafer or the damaged area of the wafer surface, thereby reducing the light loss of the wafer; but since the explosion point 11 is formed inside the substrate 10, it is formed during the formation. The material of the explosion point 11 region is ablated by the laser and adheres to the sidewall of the explosion point 11, thereby blocking the emission of light and affecting the external quantum efficiency of the light emitting diode.

 technical problem

 Problem solution

 Technical solution

 [0004] In view of the above problems, the present invention provides a back shaving method in an LED process and a forming structure thereof. First, a plurality of impurity releasing holes are formed on a back surface of a substrate by laser focusing, and then further utilized along the position of the impurity releasing holes. The laser stealth cutting technology forms a plurality of invisible cutting blast points, so that the impurities generated in the stealth cutting process are discharged into the substrate through the impurity releasing holes, thereby reducing the adverse effect of the ablation impurities adhering to the side wall of the stealth cutting blasting point and improving the brightness. The external quantum efficiency of the LED.

[0005] The technical solution to solve the above problems is as follows: A back shaving method in an LED process includes the following steps: 1) providing a substrate, growing an epitaxial layer on the surface of the substrate, and fabricating a plurality of LED units 2) focusing on the back surface of the substrate by using a laser to form a plurality of impurity releasing holes; 3) focusing on the inside of the substrate by a laser at a position corresponding to the impurity releasing hole to form a stealth cutting blast point, Make the miscellaneous The quality release hole is connected with the stealth cutting blast point to discharge impurities generated during the formation of the stealth cutting blast point through the impurity releasing hole to prevent the impurities from adhering to the sidewall of the stealth cutting blasting point and reducing the external quantum of the LED unit. effectiveness.

 Preferably, the impurity-releasing holes formed in the step 2) are located between the adjacent LED units with a vertical extension line toward the epitaxial layer.

 [0007] Preferably, the impurity release hole in the step 3) is on the same axis as the stealth cutting explosion point.

 [0008] Preferably, the substrate is any one of a sapphire flat substrate, a patterned sapphire substrate, a silicon substrate, a silicon carbide substrate, a gallium nitride substrate, and a glass substrate.

[0009] Preferably, the back surface of the substrate further has a reflective layer, and the reflective layer is a multilayer structure composed of a metal reflective layer, a distributed Bragg reflection layer or a metal reflective layer and a distributed Bragg reflection layer.

[0010] Preferably, the metal reflective layer is an A1 layer, an Ag layer, and an Au layer.

 [0011] forming a light emitting diode structure using the above-described cutting method, including a substrate, the structure including a plurality of impurity releasing holes on a back surface of the substrate and a stealth cutting blast point located inside thereof, the impurity releasing hole and The stealth cutting blast points are located on the same axis and are in communication with each other, and the impurities released during the formation of the stealth cutting blast point are discharged through the impurity releasing holes.

 [0012] Preferably, the substrate is any one of a sapphire flat substrate, a sapphire patterned substrate, a silicon substrate, a silicon carbide substrate, a gallium nitride substrate, and a glass substrate.

 [0013] Preferably, the impurity release hole is located between adjacent LED units along a vertical extension line of the epitaxial layer.

[0014] The present invention also provides a gallium nitride-based light-emitting diode chip and a preparation method thereof, which can fully utilize the advantages of stealth cutting, and effectively discharge by-products such as burn marks and debris left after laser stealth cutting. , reduce the light absorption of by-products, increase the light output of the side wall of the light-emitting diode, and improve the light-emitting efficiency.

 [0015] A method for preparing a gallium nitride based light emitting diode chip, comprising the steps of: (1) providing a substrate;

(2) forming an epitaxial layer on the substrate; (3) obtaining ablation holes by laser stealth cutting inside the substrate; (4) fabricating P and N electrodes through a mask and an etching process; (5) being ground And the cleaving process, the LED chip is prepared; wherein the step (3) of the laser stealth cutting is focused at a position of 10 μηι to 40 μιη from the back of the substrate, and the laser energy is adjusted to 0.32 W to 0.6 W, and the laser frequency is adjusted. 15KHz~4 ΟΚΗζ, so that the laser stealth cutting ablate in the substrate to form a hole penetrates to the back of the exposed substrate, which is good for burning Traces, debris by-products are discharged, reducing light absorption.

[0016] Preferably, the epitaxial layer comprises an N-GaN layer, a light emitting layer and a P-GaN layer.

[0017] Preferably, the epitaxial layer is provided with a dicing channel of a network structure.

[0018] Preferably, the cutting lane is composed of a longitudinal straight cutting channel and a transverse straight cutting channel.

[0019] Preferably, the laser invisible cutting is consistent with the position of the cutting track in the vertical direction in the substrate.

 [0020] Preferably, the pitch of the holes is 8 μm to 20 μm, and the size of the holes is 1 μm to 4 μm.

 [0021] Preferably, the back surface of the substrate is provided with a distributed Bragg reflection layer.

 Advantageous effects of the invention

 Beneficial effect

 [0022] In the back-wiping method in the foregoing LED process, an impurity release hole is first formed on a back surface of a substrate having a plurality of LED units, and then a laser is focused on the inside of the substrate at a position corresponding to the impurity release hole to form an invisible shape. Cutting a blast point, connecting the impurity release hole and the stealth cutting blast point to discharge impurities generated during the formation of the stealth cutting blast point through the impurity releasing hole to prevent the impurity from adhering to the sidewall of the stealth cutting blasting point The external quantum efficiency of the LED unit is reduced. Compared with the prior art, only the invisible cutting blast point is formed inside the substrate, the invention utilizes the contact stealing blasting point and the impurity releasing hole on the back surface of the substrate to further reduce the substrate non- Anomalous phenomena such as oblique cracks generated in the subsequent rupture process of the blasting point region improve product yield.

 [0023] In the foregoing method for fabricating a gallium nitride-based light-emitting diode chip, by focusing at a position 10 μm to 50 μm from the back surface of the substrate, the laser energy is increased, and the laser frequency is adjusted, so that the laser stealth cutting ablates in the substrate to form a hole. Throughout the exposed back surface of the substrate, effectively discharging the by-products such as burn marks and debris left after the laser stealth cutting, reducing the absorption of light by the by-products, increasing the light output of the sidewall of the light-emitting diode, and improving the light-emitting efficiency; The bottom and the hole have different refractive indexes, and the laser ablation scratch is similar to the side of the LED chip, which increases the angle of light extraction, thereby increasing the axial light, thus improving the overall luminous efficiency of the LED chip; By effectively discharging the by-products left after the laser stealth cutting, the subsequent chemical solution removal process is omitted, and the manufacturing cost is effectively saved.

 Brief description of the drawing

DRAWINGS The drawings are intended to provide a further understanding of the invention, and are intended to be a part of the description of the invention. In addition, the drawing figures are a summary of the description and are not drawn to scale.

 1 is a side view of an LED wafer after the formation of a stealth cutting burst in the prior art.

 2 to 3 are schematic flowcharts of a back shading method according to Embodiment 1 of the present invention.

 4 is a back view of a substrate according to Embodiment 1 of the present invention.

 5 to 7 are schematic cross-sectional views showing the back shaving method of Embodiment 2 of the present invention.

 8 to FIG. 11 are schematic cross-sectional views showing a process of fabricating a gallium nitride-based light-emitting diode chip according to Embodiment 3 of the present invention. [0030] FIG. 12 is a schematic structural view of a gallium nitride-based light-emitting diode chip of Embodiment 4.

 [0031] In the drawing: 10: substrate; 11: stealth cutting blast point; 12: impurity releasing hole; 20: epitaxial layer; 30: reflective layer; 31: impurity releasing hole two; 101: patterned sapphire substrate; : N-GaN layer; 103: light-emitting layer; 104: P-GaN layer; 105: hole; 106: P electrode; 107: N electrode; 108: distributed Bragg reflection layer; A: transverse straight line cutting; B: longitudinal straight line cutting line.

Embodiments of the invention

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings and embodiments.

Embodiment 1

[0034] Referring to FIGS. 2 to 4, a back-wiping method for an LED process according to the present invention specifically includes the following steps. First, a substrate 10 is provided, an epitaxial layer is grown on the upper surface of the substrate 10, and a plurality of LED units are fabricated. 20. The substrate 10 may be any one of a sapphire flat substrate, a sapphire patterned substrate, a silicon substrate, a silicon carbide substrate, a gallium nitride substrate, and a glass substrate, during mass production of the LED. Preferably, the sapphire substrate is patterned; then, a laser is used to focus on the back surface of the substrate 10 to form a plurality of impurity releasing holes 12, wherein the impurity releasing holes 12 preferably have a pore diameter range of 1 to 6 μm, and the impurity releasing holes 12 face the epitaxial layer. The vertical extension line is located between the adjacent LED units 20; then, at a corresponding position with the impurity release hole 12, a laser is focused on the inside of the substrate 10 to form a stealth cutting blast point 11, the impurity releasing hole 12 and the stealth cutting blast Point 11 is connected to discharge impurities generated during the formation of the stealth cutting blast point 11 through the impurity releasing hole 12 to prevent the impurities from adhering to the sidewall of the stealth cutting blasting point 11 to reduce the external quantum efficiency of the LED unit; and invisible cutting Burst point 11 On the same axis as the impurity releasing hole 12, in the process of the front side lobes of the subsequent LED, a plurality of mutually independent LED units can be separated along the vertical straight position where the impurity releasing hole 12 and the stealth cutting blast point 11 are located.

 [0035] In the prior art, some technicians remove the ablation impurities attached to the sidewall by using a blade or other tools, and not only a large amount of manpower is required in the removal process, but also the operation tool is easy to damage the surface of the LED epitaxial layer and reduce the quality of the LED. And not suitable for large-scale production needs. The present invention forms an impurity releasing hole 12 penetrating between the back surface of the substrate 10 and the invisible cutting blast point 11 before the formation of the stealth cutting blast point 11, and the impurity releasing hole 12 is directly used to release the invisible cutting blast point 11 during formation. Impurity, this method only increases the formation of impurity release holes 12 in the back-draw process, reducing the probability of damage to the LED surface, saving labor costs; meanwhile, forming a stealth cutting blast point only inside the substrate 10 in the prior art In contrast, the present invention utilizes the invisible cut blasting point 11 and the impurity releasing hole 12 on the back surface of the substrate, thereby further reducing the abnormal phenomenon such as the oblique crack generated in the non-cutting blasting area of the substrate 10 in the subsequent splicing process, and improving the product. Yield.

 Embodiment 2

 [0037] Referring to FIGS. 5-7, the difference between this embodiment and Embodiment 1 is that a reflective layer 30 is deposited on the back side of the substrate 10, and then the reflective layer 30 corresponding to the gap position of each LED unit 20 is removed to form The impurity releasing hole 23 in the reflective layer 30, the reflective layer 30 is a multilayer structure composed of a metal reflective layer, a distributed Bragg reflection layer or a metal reflective layer and a distributed Bragg reflection layer, wherein the metal reflective layer is an A1 layer, an Ag layer or an Au layer. In this embodiment, a distributed Bragg reflection layer having a high reflectance is preferred; subsequently, an impurity release hole 12 is formed on the surface of the substrate 10 by laser focusing on the corresponding positions of the impurity release holes 31, and a stealth cut point 11 is formed by stealth cutting. In the subsequent process of the front side lobes of the LED, a plurality of mutually independent LED units 20 can be separated along the vertical straight position where the impurity releasing holes 31, the impurity releasing holes 12 and the stealth cutting blast points 11 are located.

 Embodiment 3

 [0039] The embodiment provides a method for fabricating a gallium nitride light emitting diode chip, and the manufacturing steps thereof include: [0040] As shown in FIG. 8, metal organic chemical vapor deposition (MOCVD) is performed on the patterned sapphire substrate 101. Epitaxial growth is sequentially performed: an N-GaN layer 102, a light-emitting layer 103, and a P-GaN layer 104.

As shown in FIG. 9, the laser is drawn along the surface of the epitaxial layer, the longitudinal straight scribe line B is formed in a direction perpendicular to the flat side, and the transverse straight scribe line A is formed in a direction parallel to the flat side, and the scribe lines A and B are formed. The cutting path of the network structure. [0042] As shown in FIG. 10, the laser stealth cutting is performed at a position of 10 μm to 40 μm from the back surface of the substrate, and the laser energy is adjusted to 0.32 W to 0.6 W, and the laser frequency is adjusted from 15 kHz to 40 kHz, and the laser stealth cutting ablation is performed. The position is vertically aligned with the position of the dicing line, so that the laser stealth cutting is ablated in the substrate to form the hole 105 to penetrate the back surface of the substrate, which is favorable for burn marks, waste by-product discharge, and reduced light absorption; The hole 105 has a pitch of 8 μm to 20 μm, and the hole has a size of 1 μm to 4 μm. The refractive index of the substrate 101 and the ablation hole 105 are different, and the laser ablation scratch is similar to the surface of the LED chip, which is increased. The angle of light extraction, thereby achieving the purpose of increasing axial light, thus improving the overall luminous efficiency of the LED chip; effectively eliminating the by-products left after the laser stealth cutting, eliminating the subsequent chemical solution removal process, and effectively saving manufacturing costs .

 [0043] As shown in FIG. 11, a P electrode 106 and an N electrode 107 are formed on the P-GaN layer 104 and the exposed N-GaN layer 102 by a mask and an etching process; and are obtained by a grinding and cleaving process. LED chip.

 [0044] The GaN-based light-emitting diode chip prepared in this embodiment has high luminous efficiency and excellent quality compared with a chip prepared by a conventional process.

 [0045] Example 4

 As shown in FIG. 12, unlike the third embodiment, the present embodiment provides a distributed Bragg reflection layer 108 on the back surface of the substrate, so that the light extraction efficiency of the LED chip is further improved. It should be noted that the distribution Bragg reflection layer 108 may be prepared before laser invisible cutting inside the substrate, or after ablation holes are obtained by laser invisible cutting inside the substrate.

 [0047] It is to be understood that the above-described embodiments are a preferred embodiment of the present invention, and the scope of the present invention is not limited to the embodiments, and any modifications made in accordance with the present invention are within the scope of the present invention.

Claims

Claim  [Claim 1] A method of fabricating a light emitting diode, comprising the steps of:  1) providing a substrate, growing an epitaxial layer on the surface of the substrate and fabricating a plurality of LED units 2) focusing on a back surface of the substrate by using a laser to form a plurality of impurity releasing holes; 3) at a position corresponding to the plurality of impurity releasing holes, focusing on the inside of the substrate by using a laser to form a plurality of invisible cutting blast points, so that the impurity releasing holes and the stealth cutting blast point are connected to be invisible Impurities generated during the formation of the cut-off point are discharged through the impurity-releasing hole to the inside of the substrate, and impurities are prevented from adhering to the sidewall of the invisible cut-off point to reduce the external quantum efficiency of the LED unit.  [Claim 2] The method for fabricating a light emitting diode according to claim 1, wherein: the impurity release hole formed in the step 2) is located between the adjacent LE D cells with a vertical extension line toward the epitaxial layer. .  [Claim 3] The method for fabricating a light emitting diode according to claim 1, wherein the impurity releasing hole in the step 3) is located on the same axis as the stealth cutting blast point. [Claim 4] The method for fabricating a light emitting diode according to claim 1, wherein: the substrate is a sapphire flat substrate, a patterned sapphire substrate, a silicon substrate, a silicon carbide substrate, and nitriding Any one of a gallium substrate and a glass substrate.  [Claim 5] The method for fabricating a light emitting diode according to claim 1, wherein: the back surface of the substrate further has a reflective layer, and the reflective layer is a metal reflective layer, a distributed Bragg reflection layer or a metal reflective layer. A multilayer structure consisting of a distributed Bragg reflector.  [Claim 6] The method of manufacturing a light emitting diode according to claim 5, wherein the metal reflective layer is an A1 layer, an Ag layer or an Au layer. [Claim 7] A light emitting diode comprising a substrate, wherein: the structure is prepared by the method of claims 1 to 6. [Claim 8] The light emitting diode according to claim 7, wherein: the structure includes a plurality of impurity releasing holes on a back surface of the substrate and a stealth cutting blast point inside the substrate, the impurities The release hole and the invisible cutting blast point are on the same axis and are connected to each other. The impurities released during the formation of the stealth cutting blast are discharged through the impurity releasing holes to the inside of the substrate.  [Claim 9] A light emitting diode according to claim 7, wherein: the substrate is a sapphire flat substrate, a sapphire patterned substrate, a silicon substrate, a silicon carbide substrate, a gallium nitride liner Any of the bottom and glass substrates.  [Claim 10] The light emitting diode according to claim 7, wherein: the impurity releasing holes are located between adjacent LED units toward a vertical extending line of the epitaxial layer. [Claim 11] A method for preparing a light emitting diode, comprising the steps of:  (1) providing a substrate;  (2) forming an epitaxial layer on the substrate;  (3) ablation holes are obtained by laser stealth cutting inside the substrate;  (4) Making P and N electrodes through a mask and an etching process;  (5) After the grinding and cleaving process, the LED chip is obtained;  The method is characterized in that: step (3) the laser stealth cutting is focused at a position of 10μηι~4 Ομηι from the back of the substrate, adjusting the laser energy to 0.32W~0.6W, and adjusting the laser frequency at 15K Hz~40KHz, so that the laser is invisible. The cutting is ablated in the substrate to form a hole penetrating through the exposed back surface of the substrate to facilitate burn marks, debris by-product discharge, and reduced light absorption.  [Claim 12] The method of manufacturing a light emitting diode according to claim 11, wherein the epitaxial layer comprises an N-GaN layer, a light emitting layer, and a P-GaN layer. [Claim 13] The method of manufacturing a light emitting diode according to claim 11, wherein the epitaxial layer is provided with a dicing line of a network structure. [Claim 14] The method of manufacturing a light emitting diode according to claim 13, wherein the cutting path is constituted by a longitudinal straight cut track and a lateral straight cut track. [Claim 15] The method for fabricating a light emitting diode according to claim 13, wherein: the laser invisible cutting is vertically aligned with the position of the cutting track in the vertical direction in the substrate. [Claim 16] The method for fabricating a light emitting diode according to claim 11, wherein: the pitch of the holes is 8 μm to 20 μm. A method of manufacturing a light emitting diode according to claim 11, wherein the size of the hole is 1 μm to 4 μm. [Claim 18] The method of manufacturing a light emitting diode according to claim 11, wherein the back surface of the substrate is provided with a distributed Bragg reflection layer. [Light emission diode] A light-emitting diode, which is produced by the production method according to any one of claims 11 to 18.